In recent years, the image recording material is predominated particularly by a material for forming a color image. More specifically, a recording material using an ink jet system, a recording material using a heat-sensitive transfer system, a recording material using an electro-photographic system, a silver halide light-sensitive material using a transfer system, a printing ink, a recording pen and the like are popularly used. Also, a color filter for recording/reproducing a color image is used in an image pick-up element such as CCD of photographing equipment, or in LCD or PDP of display. In these color image recording materials or color filters, three primary color dyes (dyes or pigments) by a so-called additive or subtractive color mixing method are used for reproducing or recording a full color image, however, a dye having absorption properties capable of realizing a preferred color reproduction region and having fastness capable of enduring various use and environmental conditions is not found at present and improvements are keenly demanded.
The ink jet recording method has been abruptly spread and is further growing because the material cost is low, high-speed recording can be obtained, noises are less generated at the recording and color recording is easy. The ink jet recording method includes a continuous system of continuously jetting out a liquid droplet and an on-demand system of jetting out a liquid droplet according to image information signals, and the ejection system therefore includes a system of ejecting a liquid droplet by generating bubbles in ink using heat, a system of using an ultrasonic wave, and a system of ejecting a liquid droplet by suction using an electrostatic force. The ink used for ink jetting includes an aqueous ink, an oily ink and a solid (fusion-type) ink.
The dye used in the ink for ink jetting is required to have good solubility or dispersibility in a solvent, enable high-density recording, provide good (color) hue, have fastness to light, heat and active gas in environment (for example, oxidative gas such as NOx and ozone, and SOx), exhibit excellent resistance against water and chemicals, ensure good fixing property to an image-receiving material to cause less blurring, give an ink having excellent storability, have no toxicity and high purity and be available at a low cost.
In particular, the dye is strongly demanded to have good cyan color and fastness to light, humidity and heat and when printed on an image-receiving material having an ink-accepting layer containing a porous white inorganic pigment particle, be resistant against oxidative gas such as ozone in the environment.
A representative skeleton of the cyan dye used for ink is a phthalocyanine or triphenylmethane structure. Representative examples of the phthalocyanine compound which has been reported and is used over the widest range include phthalocyanine derivatives classified into the following (1) to (6):    (1) copper phthalocyanine compounds such as Direct Blue 86 and Direct blue 87 [for example, Cu-Pc-(SO3Na)m: a mixture of m=1 to 4] (hereinafter, Pc means a phthalocyanine skeleton);    (2) Direct Blue 199 and phthalocyanine dyes described in JP-A-62-190273 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), JP-A-63-28690, JP-A-63-306075, JP-A-63-306076, JP-A-2-131983, JP-A-3-122171, JP-A-3-200883, JP-A-7-138511, etc. [for example, Cu-Pc-(SO3Na)m(SO2NH2)n: a mixture of m+n=1 to 4];    (3) phthalocyanine-base dyes described in JP-A-63-210175, JP-A-63-37176, JP-A-63-304071, JP-A-5-171085, WO00/08102, etc. [for example, Cu-Pc-(CO2H)m(CONR1R2)n: a mixture of m+n=0 to 4];    (4) phthalocyanine-base dyes described in JP-A-59-30874, JP-A-1-126381, JP-A-1-190770, JP-A-6-16982, JP-A-7-82499, JP-A-8-34942, JP-A-8-60053, JP-A-8-113745, JP-A-8-310116, JP-A-10-140063, JP-A-10-298463, JP-A-11-29729, JP-A-11-320921, EP-A-173476, EP-A-468649, EP-A-559309, EP-A-596383, German Patent 3,411,476, U.S. Pat. No. 6,086,955, WO99/13009, British Patent Publication 2,341,868A, etc. [for example, Cu-Pc-(SO3H)m(SO2NR1R2)n: a mixture of m+n=0 to 4, and m≠0];    (5) phthalocyanine-base dyes described in JP-A-60-208365, JP-A-61-2772, JP-A-6-57653, JP-A-8-60052, JP-A-8-295819, JP-A-10-130517, JP-A-11-72614, Japanese Unexamined Published International Application Nos. 11-515047 and 11-515048, EP-A-196901, WO95/29208, WO98/49239, W098/49240, W099/50363, W099/67334, etc. [for example, Cu-Pc-(SO3H)l(SO2NH2)m(SO2NR1R2)n: a mixture of 1+m+n=0 to 4]; and    (6) phthalocyanine-base dyes described in JP-A-59-22967, JP-A-61-185576, JP-A-1-95093, JP-A-3-195783, EP-A-649881, WO00/08101, WO00/08103, etc. [for example, Cu-Pc-(SO2NR1R2)n: a mixture of n=1 to 5].
Phthalocyanine-base dyes widely used in general at present, represented by Direct Blue 87 and Direct Blue 199, are excellent in the light fastness as compared with generally known magenta dyes, yellow dyes and triphenylmethane-base cyanine dyes.
However, the phthalocyanine-base dyes provide a greenish (color) hue under acidic conditions and are improper for a cyan ink. In the case of using these dyes for a cyanine ink, these are most suitably used under conditions from neutral to alkaline. However, even if the ink is in the region from neutral to alkaline, when the material on which an image or the like is recorded is an acidic paper, the (color) hue of the printed matter may greatly change.
Furthermore, discoloration to a greenish (color) hue or decoloration occurs due to oxidative gases such as nitrogen oxide gas and ozone, which are often taken as a problem also from an environmental issue, and this simultaneously causes reduction in the printing density.
On the other hand, triphenylmethane-base dyes provide a good (color) hue but are very inferior in the light fastness, resistance against ozone gas and the like.
If the use field hereafter expands and the printed matter is widely used for exhibition such as advertisement, the case of being exposed to light or active gas in the environment increases and to cope with this, a dye and an ink composition having light fastness and excellent resistance against active gases (for example, oxidative gas such as NOx and ozone, and SOx) in the environment are more strongly demanded.
However, it is very difficult to find out a cyan dye (for example, phthalocyanine-base dye) and a cyan ink satisfying these requirements in a high level.
As for the ink for an ink jet recording system, an aqueous dye ink obtained by dissolving a water-soluble dye of various types in a liquid medium comprising water and a water-soluble organic solvent, an aqueous pigment ink obtained by dispersing a pigment of various types in a liquid medium comprising water and a water-soluble organic solvent, an oily dye ink obtained by dissolving an oil-soluble dye in an organic solvent, and the like are known. Among these inks, the aqueous ink obtained by dissolving an aqueous dye is excellent in the safety because the main solvent is water, enables good coloring of a color image and formation of a high-grade printed image because a dye is used, and also exhibits excellent ink storage stability. Therefore, this aqueous ink is predominating as an ink for ink jet recording.
The phthalocyanine-base dyes imparted with water solubility are heretofore disclosed, for example, in WO00/08102, JP-A-2000-303014 and JP-A-2000-313837, however, none of these dyes have succeeded in satisfying both the (color) hue and the fastness to light and oxidative gas. A cyan ink product fully satisfying the requirements on the market is not yet provided.
When a recorded image having a high optical density is formed, this is accompanied with a problem that as the image is dried, the dye crystal deposits on the surface of the recording material and the recorded image reflects light to cause a so-called bronze phenomenon of emitting metallic gloss. This phenomenon is considered to readily occur when the water solubility of dye is decreased so as to improve water resistance or an amino group of a hydrogen bond group is introduced into the dye structure, because the dye is elevated in the associating (aggregating) property. The generation of bronze phenomenon not only incurs decrease in the optical density of the recorded image but also causes great difference from the desired (color) hue of the recorded image. Therefore, it is one of important performances required of the ink for ink jetting to prevent the bronze phenomenon.
Known examples of the method for preventing the bronze phenomenon include a method of adding a specific nitrogen-containing compound (see, for example, JP-A-55-120676, JP-A-62-119280, JP-A-64-6072, JP-A-1-152176, JP-A-2-41369, JP-A-5-125311, JP-A-6-25575, JP-A-6-128515, JP-A-6-228476, JP-A-6-228483, JP-A-6-248212, JP-A-7-228810, JP-A-7-268261, JP-A-8-259865, JP-A-9-12944, JP-A-9-12946, JP-A-9-12949 and JP-A-10-36735) and a method of adding a specific titanium compound (see, JP-A-8-337745). The bronze phenomenon may be prevented from occurring by adding these compounds, however, there is a fear that the additives decrease various performances of ink and the quality of recorded image. For example, as described in JP-A-8-259865, when an alkanolamine is added to the ink, the bronze phenomenon can be prevented but by the addition only in a small amount, the pH of ink increases to 11 or more and the high pH ink not only adversely affects nozzles but also lacks in safety on erroneously contacting with a human body and moreover, decreases the printing grade or water resistance of the recorded image.
Other than these, examples of the method for improving the performance of ink for ink jetted by using an additive are described in JP-A-5-339532 and JP-A-2001-254040 where an anionic additive except for dyes, having lithium ion, quaternary ammonium ion or quaternary phosphonium ion as the counter cation is added and thereby, even when the counter ion of the dye is not such ion, an effect of preventing clogging is obtained because the solubility is improved. On the other hand, JP-A-7-26178 describes a technique where an alkali metal compound is added to ink and thereby, the production of an aggregate of dye is prevented, as a result, the viscosity of ink does not increase. However, in JP-A-1036735, it is pointed out that this improvement effect can be attained when the storage time is short, but when stored for a long period of time, the storage stability has a problem.
As such, various effects can be obtained by using additives, however, various performances can be hardly maintained if additives are used. Particularly, in the case where the solubility and aggregating property of dye must be taken account of, selection of the kind and amount of additive is difficult. In using an ionic additive, the effect thereof on the counter ion must also be taken into consideration. Accordingly, a substantial bronze phenomenon-inhibiting method not relying on additives is preferred.
Studies are being aggressively made with an attempt to improve various performances required of the ink for ink jetting by changing the counter ion for the ionic hydrophilic group of metal phthalocyanine compounds and examples thereof include JP-A-5-339532, JP-A-6-16982, JP-A-6-248212, JP-A-6-322286, JP-A-7-138511 and JP-A-10-130517.
For example, in JP-A-57-202358, JP-A-63-81179, JP-A-63-317568 and Japanese Patents 2581769 and 3163176, lithium ion is referred to as preferred counter ion for the ionic hydrophilic group of metal phthalocyanine dyes and it is stated that this ion is effective for providing an ink having high concentration, storage stability and jetting stability. On the other hand, JP-A-7-82499 states that lithium ion is not preferred as the counter cation, because the water resistance of the recorded image decreases due to high water solubility of the dye. From these, it is seen that the performances required of the ink for ink jetting cannot be easily satisfied merely by changing the counter salt.
As described above, an ink capable of satisfying all of various performances required of the water-soluble ink for ink jetting is not yet found at present.
Problems to be Solved by the Invention:
The present invention has been made to solve those problems in conventional techniques and achieve the following objects. That is, the objects of the present invention are
(1) to provide a novel ink having absorption properties ensuring excellent color reproduction as a dye for three primary colors and at the same time, having sufficiently high fastness to light, heat, humidity and active gas in the environment;
(2) to provide an ink of giving a colored image or colored material excellent in the (color) hue and the fastness, for example, an ink composition for printing such as ink jetting;
(3) to provide an ink for ink jet recording and an ink jet recording method, which can form an image having good (color) hue by the use of a phthalocyanine compound derivative, having high fastness particularly against ozone gas and free of generation of a bronze phenomenon; and
(4) to provide a method for forming an image having fastness by using the above-described ink jet recording method and thereby improving the ozone gas discoloration resistance of the image recorded material.
Means to Solve the Problems:
As a result of extensive investigations on phthalocyanine derivatives of providing good (color) hue, generating no bronze phenomenon and ensuring fastness to light and gas (particularly ozone gas), the present inventors have found that the above-described objects can be attained by a phthalocyanine compound where the counter cation of the ionic hydrophilic group is lithium ion, particularly a phthalocyanine compound represented by the following formula (I), having (1) a specific spectral absorption curve and (2) a specific dye structure (specific substituents are introduced into specific substitution sites in a specific number of substituents), more particularly, a phthalocyanine compound represented by formula (II) or (III).